This application relates to magnetic disc drives and more particularly to an improved disc drive clamp and disc drive spindle motor apparatus for mounting information storage disc within the disc drive.
Disc drives are data storage devices that store digital data in magnetic form on a storage medium on a rotating information storage disc. Modern disc drives include one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks typically by an array of transducers (xe2x80x9cheadsxe2x80x9d) mounted to a radial actuator for movement of the heads relative to the discs. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The read/write transducer, e.g., a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment. Critical to both of these operations is the accurate locating of the head over the center of the desired track.
The heads are mounted via flexures at the ends of a plurality of actuator arms that project radially outward from the actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs.
Spindle motor assemblies often utilize a rotating spindle hub journaled to a non-rotatable spindle shaft. A disc clamp is typically secured to the rotating spindle hub to exert a downward axial force on the mounted information storage discs and disc spacers in order to securely fasten the discs and spacer together on the hub. Typically, the disc clamp is basically an annular leaf spring that is sized such that its outer rim exerts the downward force through a series of equally spaced screws positioned around the central portion of the clamp and torqued through holes in a central portion of the clamp into the spindle hub. The spaced radial positioning of the screws is beneficial for exerting a distributed clamping force on the stacked discs on the spindle assembly because the force is exerted at the periphery of the clamp in closer proximity to the mounted information storage discs and disc spacers. However, the screw is a discrete source of the clamping force, thus the distribution of the downward force around the periphery of the clamp, against the adjacent disc is exerted in a non-uniform manner. Non-uniform clamping force can generally cause variations in the load force applied and, as a result, can cause the top mounted information storage disc to be physically distorted. Distortion of the top disc, even by as little as 100 micro inches, can lead to generation of unacceptable operational errors during recording and reproduction of data on the information storage disc.
In a second type of spindle motor assembly the spindle shaft and spindle hub portion both rotate about a bearing sleeve. Here, a single screw can be used to secure the disc clamp to the rotating spindle shaft because the shaft rotates with the screw (as opposed to the non-rotatable shaft where a plurality of screws must be positioned in the hub about the shaft). However, in order to develop a clamping force with a single screw similar to the force developed by the plurality of screws surrounding the non-rotatable shaft, it is necessary to apply a much higher torque to the single screw. This relatively high torque requirement can lead to a number of problems including over-stressing the spindle shaft bearing, stripping threads, and the generation of particles during the torquing process. These high-torque related problems can damage the bearing and lead to failure of the spindle motor.
Some screw-less disc clamps have been developed in attempts to overcome these shortcomings, but without completely satisfactory results. Often, such screw-less clamps are complicated, and difficult and expensive to manufacture and use. One problem in many screw-less disc clamps is the inability to provide a simple and easy to use mechanism by which a disc clamp can be centered about the spindle to provide a generally uniform clamping force.
Currently, there is a need in the relevant art to overcome the shortcomings of the traditional single screw disc drive spindle motor assembly, as well as the non-rotatable multiple screw spindle shaft spindle motor. There is also a need in the art to overcome the shortcomings of the screw-less disc clamp technology that currently exists.
Against this backdrop the present invention has been developed. The present invention is an apparatus and method for uniformly retaining information storage discs onto a spindle motor in a disc drive.
In accordance with one preferred embodiment, the invention is implemented as a disc drive spindle motor assembly including a spindle and a hub portion extending radially outward from the spindle, the hub portion defining a top surface. An information storage disc is mounted on the hub portion, the information storage disc having a top surface. The assembly further includes an annular disc clamp forming a central aperture, having a middle annular raised portion, an outer annular peripheral portion, and at least one inner centering portion including an inner vertical peripheral surface. The central aperture of the disc clamp is sized to receive the spindle to allow the inner centering portion to center the disc clamp about the spindle, while the outer peripheral portion engages the top surface of the information storage disc, and the middle annular raised portion extends above the top surface of the hub portion and is adapted to receive a downwardly directed force. A disc clamp retainer applying this force is connected to the spindle. The disc clamp retainer is fastened to the spindle and engages the middle annular raised portion of the disc clamp to transmit this force through the outer peripheral portion to the disc.
The invention can be implemented in accordance with another preferred embodiment as a disc clamp having several discrete tabs forming the inner centering portion adapted to center the disc clamp on the spindle.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.